Conventionally, a wafer transfer device is known, which includes a hand which holds the peripheral edge portion of a wafer which is a substrate material of a semiconductor device, and a robot body on which this hand is attached. As this kind of wafer transfer device, for example, Patent Literatures 1 and 2 disclose a wafer transfer device configured to transfer the wafer with a vertical posture in which the wafer is vertically oriented. The term “vertical posture” means that the primary (main) surface of the wafer faces substantially horizontally.
Patent Literature 1 discloses a wafer transfer hand including a fixed element disposed below the wafer, a movable element which is disposed above the wafer and is advanceable to and retractable from the wafer, and a frame on which these elements are attached. This wafer transfer hand is configured to hold the peripheral edge portion of the wafer with the vertical posture, by use of the fixed element and the movable element.
Patent Literature 2 discloses a wafer holding device including two front-side (near-side) pads disposed at a front side of the wafer and at upper and lower sides in such a manner that a horizontal line extending through the center of the wafer is interposed between the two pads, a back-side (far-side) pad disposed at a back side of the wafer and above the horizontal line extending through the center of the wafer, and an end effector having a tip end on which the back-side pad is attached.
Patent Literature 2 further discloses a wafer container which can store therein a plurality of wafers in a state in which the wafers have a vertical posture and are horizontally arranged with predetermined gaps. In the interior of this wafer container, a plurality of V-shaped grooves which are horizontally arranged with predetermined gaps are provided in a back wall and a floor. The peripheral edge portion of each of the plurality of wafers is fitted into the groove of the back wall and the groove of the floor. In this way, the wafer is held in the wafer container which can store therein the wafers vertically placed.